(1) Field of the Invention
This invention relates to semiconductor device package, particularly to light emitting diode (LED) package.
(2) Brief Description of the Prior Art
FIG. 1 shows the top view of a tri-color light emitting diode module for providing the back-light for a display panel. An insulating substrate 10 is plated with four separate metallic plates, 11, 12, 13 and 14. A red LED chip 111 has a bottom electrode mounted on the metal plate 11 and a top electrode wire bonded to the common metal plate 14. The green LED chip 112 is mounted on the metal plate 12 and has two top electrodes. One of the electrodes is wire-bonded to metal plate 12, and another electrode is wire-bonded to the common metal plate 14. The blue LED chip 113 is mounted on the metal plate 13 and has two top electrodes. One of the electrodes is wire-bonded to metal plate 13 and another electrode is wire-bonded to the common metal plate 14. The metal plates 11, 12, 13, 14 are wrapped around the corners 121, 122, 123, 124 of the substrate 10 respectively to reach the bottom of the substrate. FIG. 1 illustrates that the LEDs can have both electrodes on top of the chip or have one top electrode and one bottom electrode. While the tri-color LEDs are illustrated to produce full color, it should be pointed out that two color LEDs, eg. red and green, may also be used to produce red, green, yellow and other mixed colors. When two color LEDs are used, only three metal plates (i.e. one more than the number of LEDs) need be used.
FIG.2 shows the bottom view of the substrate. The extensions of the plates 11, 12, 1314 at the top surface of the substrate 10 wrapping around the corners 121, 122, 123, 124 respectively become contacts 21, 22, 23, 24 respectively. The contacts are suitable for surface mounting of the LED module to a motherboard.
When such a LED module is used as the back light of a display, the prior art system is shown in FIG. 7. The color module 15 described in FIGS. 1 and 2 is mounted over a plate which is parallel to the display panel 19. The light emitted vertically from module 15 is reflected by a mirror 16 to a light conducting plate 18. The light from the light conducting plate is diffused by a translucent plate 19 to serve as the back light for the display panel 19. In such a system, a mirror is needed to reflect the color lights, because the lights emitted from the module 16 is perpendicular to the display 19.